Assistance parsing AWS Payload

[dswider]

Hi all, I’m trying to parse a payload coming from AWS in ServiceNow, and I need some guidance on how to go about extracting a specific field. The payload looks like this: {
"statusCode": 200,
"headers": {"Content-Type": "application/json"},
"body": "{\"Operation\": \"SAVE\", \"Message\": \"SUCCESS\", \"Item\": {\"rpt\": \"INQ0000001234\", \"userId\": \"Firstname.LastName\", \"sessionID\": \"glide.scheduler.worker.4\", \"cusip\": \"000000001\", \"u_cusip_changed\": \"true\", ..."
}

I’m currently working with this script in my Scripted REST API to extract the field u_cusip_changed and update another table based on its value: 

var cusipChanged = requestBody.u_cusip_changed;
gs.info("Update Case REST cusipChanged: " + cusipChanged);

if (cusipChanged == "true") {
var caseGR = new GlideRecord('x_g_afss_inquiry_inquiries');
caseGR.addQuery('number', rptBody);
caseGR.query();

if (caseGR.next()) {
caseGR.u_cusip_changed = true;
caseGR.update();
}
}